Backpack



FIG. 1 is an isometric view of a backpack showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a back elevation view thereof;

FIG. 4 is a right elevation view thereof;

FIG. 5 is a left elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines illustrating zippers depict portions of the backpack that form no part of the claimed design. The remaining broken lines depict stitching that forms no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 